1. Technical Field
The present invention relates generally to systems for tracking moving objects and, in particular, to a self-referencing imaging tracker employing a laser designator that allows a desired target aim point to be maintained until a target kill is achieved.
2. Discussion
It is well known to use laser designators for target aim point designation. Some laser designation units are small enough to mount on the barrel of a pistol or rifle. There is a larger class of designators, however, that are used for aim point designation on targets such as tanks or aircraft. For such designators, it is necessary to provide a means for maintaining the aim point at or near a fixed place on the target as the target moves in the field. It is especially critical to maintain the laser designated aim point on the target for at least the length of time it takes to launch munitions. In conventional tracking systems, the laser designated aim point is often maintained by a human operator.
Non-imaging, laser designating trackers may also be employed using self-referencing methodologies, such as the systems disclosed in pending U.S. patent application Ser. No. 08/631,645, entitled "Laser Cross Body Tracking System and Method", and U.S. patent application Ser. No. 08/760,434, entitled "Laser Cross Body in Feature Curvature Tracker", both incorporated herein by reference.
Non-imaging self-referencing trackers are presently deployed as Vernier trackers as an adjunct to imaging trackers; that is, the trackers correct residual image jitter created by imperfect image tracker performance. Thus, the non-imaging tracker bears the major tracking burden for difficult targets, such as small artillery rounds or maneuvering cruise missiles. Non-imaging, self-referencing trackers use a laser beam to seek and hold a glint spot, typically found on a reflective curved surface such as a cylindrical missile housing.
Non-imaging laser designation devices may be combined with tracking systems. However, the conventional systems combining these techniques employ non-self-referencing open loop methods and suffer from significant limitations. The conventional devices typically require a pilot or operator to maintain the target image-laser beam glint aim point during the munitions flight. Alternatively, the location of the aim point must be inferred based on the previous movements of the target as followed and recorded by the tracker. For difficult to track targets, the conventional devices are often unable to select a vulnerable portion of the target as a desired aim point. Still other systems are unable to correct aim point errors resulting from relative motion of the tracking system or the target. Even systems employing self-referencing laser designation are susceptible to losing target lock in the event that the glint point becomes shielded or otherwise obstructed.